Wear equalized fuel delivery system

ABSTRACT

A multipump fluid delivery system that simultaneously provides pump redundancy and the large displacement necessary at low startup speeds. Valve means are provided to cause one or more pumps to recirculate unpressurized fuel during normal operation when the entire flow of the several pumps need not be pressurized to meet system demands. The valve means automatically alternates the loaded pump each successive startup. This alternate loading tends to equalize wear among the several pumps, thereby affording a longer life before fuel system overhaul is required. The valve means also simultaneously serves a pressure relief function.



1. A fluid delivery system comprising: a plurality of pumps, each of the said pumps having an inlet and an outlet; a plurality of inlet conduits respectively connected to said pump inlets for delivering fluid thereto; a plurality of discharge conduits respectively connected to said pump outlets for receiving discharge flow therefrom; a supply conduit fluidly interconnecting said discharge conduits to receive discharge flow therefrom and deliver fluid at system discharge pressure to a using device; and means automatically actuated by a predetermined decrease and subsequent predetermined increase in said system discharge pressure to bypass a discharge flow from each of said pumps in succession such that after each pressure cycle a pump different from the previously bypassed pump is bypassed.
 2. A fluid delivery system, in accordance with claim 1, wherein said automatically actuated means comprises: means to prevent reverse flows in said discharge conduits; a selector valve, having a bypass passage, positionable in a plurality of discrete positions in which fluid is bypassed through said bypass passage from at least one of said discharge conduits to said pump inlets, the number of positions being at least equal to the number of said pumps; a plurality of branch conduits fluidly interconnecting said respective discharge conduits and said selector valve, said branch conduits being fluidly connected to said discharge conduits at Respective locations intermediate said preventing means and said outlets; a pressure-sensing conduit fluidly interconnecting said selector valve and said supply conduit to transmit said system discharge pressure thereto; means fluidly connecting said selector valve to said pump inlets; and an automatic indexing device responsive to said system discharge pressure connected to said selector valve to successively position said selector valve in said discrete positions when said system discharge pressure decreases a predetermined extent and then increases a predetermined extent such that each of said pumps is successively bypassed via said bypass passage as said selector valve moves between said discrete positions.
 3. A fluid delivery system, in accordance with claim 2, wherein said selector valve includes: a housing having a bore therein and a plurality of pairs of inlet and outlet ports fluidly connected to said bore, the inlet and outlet port of each pair being respectively connected to one of said branch conduits and said pump inlet connecting means; and a piston disposed in said bore to form a chamber fluidly connected to said supply conduit, said piston containing said bypass passage, said indexing device being operatively connected to said piston to cause axial and rotational movement of said piston in said bore in response to changes in said system discharge pressure is brought into register with at least one of said pairs of inlet and outlet ports at a preselected magnitude of said system discharge pressure.
 4. A fluid delivery system, in accordance with claim 3, wherein said piston comprises: a groove adapted to fluidly communicate with at least another pair of inlet and outlet ports at another preselected magnitude of said system discharge pressure to thereby direct discharge flow from one of said pumps which is not being bypassed to said pump inlets.
 5. A fluid delivery system comprising: a plurality of pumps, each of said pumps having an inlet and an outlet; a plurality of inlet conduits respectively connected to the pump inlets for delivering fluid thereto; a plurality of discharge conduits respectively connected to the pump outlets for receiving discharge flow therefrom; a supply conduit fluidly interconnecting said discharge conduits to receive discharge flow therefrom; a plurality of check valves respectively associated with said discharge conduits intermediate said supply conduit and said outlets for preventing reverse flows in said discharge conduits; a selector valve, having a bypass passage, positionable in a plurality of discrete positions in which fluid is bypassed through the bypass passage from at least one of said discharge conduits to said pump inlets, the number of valve positions being at least equal to the number of pumps; a plurality of branch conduits fluidly interconnecting said respective discharge conduits and said selector valve, said branch conduits being fluidly connected to said discharge conduits at respective locations intermediate said check valves and said outlets; means fluidly connecting said selector valve to said pump inlets; a pressure-sensing conduit fluidly interconnecting said selector valve and said supply conduit to transmit system discharge pressure to said selector valve; and an automatic indexing device responsive to discharge pressure and connected to said selector valve to successively position said selector valve in said discrete positions when said system discharge pressure decreases a predetermined extent and then increases a predetermined extent such that each of said pumps is successively bypassed via said bypass passage as said selector valve moves between said discrete positions, said selector valve thereby serving to equalize the wear between said pumps.
 6. A fluid delivery system, in accordance with claim 5, wherein the selector valve includes: a relief groove to direct discharge flow from one of said pumps which is nOt being bypassed to said pump inlets when said system discharge pressure exceeds a predetermined value.
 7. A fluid delivery system, in accordance with claim 5, wherein said selector valve includes: a housing having a bore therein and a plurality of pairs of inlet and outlet ports fluidly connected to said bore, the inlet and outlet port of each pair being respectively connected to one of said branch conduits and said pump inlet connecting means; and a piston disposed in said bore to form a chamber fluidly connected to said supply conduit, said piston containing said bypass passage, said piston to cause axial and rotational movement of said piston in said bore in response to changes in said piston in said bore in response to changes in said system discharge pressure in said chamber such that said bypass passage is brought into register with at least one of said pairs of inlet and outlet ports at a preselected magnitude of said system discharge pressure.
 8. A fluid delivery system, in accordance with claim 7, wherein said piston comprises: a groove adapted to fluidly communicate with at least another pair of inlet and outlet ports at another preselected magnitude of said system discharge pressure to thereby direct discharge flow from one of said pumps which is not being bypassed to said pump inlets.
 9. A fluid delivery system comprising: at least two pumps, each of said pumps having an inlet and an outlet; at least two inlet conduits respectively connected to said pump inlets for delivering fluid thereto; at least two discharge conduits respectively connected to said pump outlets for receiving discharge flow therefrom; a supply conduit fluidly interconnecting said discharge conduits to receive discharge flow therefrom and deliver fluid at system discharge pressure to a using device; a valve housing having a bore therein and at least two inlet ports and at least two outlet ports in communication therewith; means respectively fluidly interconnecting said inlet ports with said discharge conduits at respective locations intermediate said pump outlets and said preventing means; means fluidly interconnecting said outlet ports and said pump inlets; a piston mounted within said bore for sliding movement therein, said piston having a bypass passage and a groove, said passage adapted to fluidly interconnect one of said inlet ports with one of said outlet ports to bypass at least one of said pumps and said groove adapted to simultaneously fluidly interconnect the other of said inlet ports with the other of said outlet ports at certain piston positions, the area of communication between said groove and said other ports increasing as said piston slides within said bore in a predetermined direction; means communicating said system discharge pressure to an end of said piston to drive said piston in said predetermined direction; spring means urging said piston in the direction opposite to said predetermined direction to bias said piston against said system discharge pressure; and means to rotate said piston within said bore during sliding movement of said piston in both said predetermined and opposite directions such that said bypass passage and said groove fluidly interconnect different inlet and outlet ports when said piston moves a certain distance opposite to said predetermined direction and then moves a certain distance in said predetermined direction. 